Astronomy and Astrophysics, volume 458, 245-257 (2006/10-4)
XMM-Newton and ESO observations of the two unidentified γ-ray sources 3EG J0616-3310 and 3EG J1249-8330.
LA PALOMBARA N., MIGNANI R.P., HATZIMINAOGLOU E., SCHIRMER M., BIGNAMI G.F. and CARAVEO P.
Abstract (from CDS):
The limited angular resolution of γ-ray telescopes prevents a direct identification of the majority of sources detected so far. This is particularly true for the low latitude, probably galactic, ones only 10% of which has been identified. Most counterparts of the identified low-latitude γ-ray sources are Isolated Neutron Stars (INS), both radio-loud and radio-quiet (Geminga-like) objects, which are characterised by an extremely high value of the X-ray-to-optical flux ratio fX/fopt. Therefore, the systematic X-ray and optical coverage of low-latitude unidentified γ-ray sources aiming at high fX/fopt sources seems one of the most promising ways to spot INS candidate counterparts. Since low latitude sources are heavily affected by the interstellar absorption at both X-ray and optical wavelengths, we have focussed on two middle-latitude, probably galactic, GRO/EGRET sources: 3EG J0616-3310 and 3EG J1249-8330. These two sources, which could belong to a local galactic population, have been selected owing to their relatively good positional accuracy, spectral shape and lack of candidate extragalactic radio counterparts. Here we report on X-ray observations of the two γ-ray error boxes performed with XMM-Newton and on their optical follow-up carried on with the Wide Field Imager at the ESO/MPG 2.2m telescope. Less than half of the ∼300 sources detected by the X-ray coverage have no optical counterparts. Among those, we have selected few interesting sources with fX/fopt≥100, which we consider promising INS candidates.
stars: neutron - gamma-rays: observations - X-rays: general
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<Available at CDS (J/A+A/458/245): table1.dat table7.dat appendix.ps chart.pdf>
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